The present invention relates to decapsulation of plastic packages of integrated circuit (IC) chips, and more particularly to a pumpless decapsulation system that supports in situ utilization.
Plastic packaging has been used for electronic devices, including semiconductor chips, for many years. To provide the plastic packaging, typically, epoxy resin is molded around the chip, a central portion of a lead frame, and bonding wires or other connections between contact pads on the chip to inner lead fingers on the lead frame. Often, decapsulation of the package, i.e., safe and effective removal of the epoxy, is desired at least in part to allow for inspection, test, and repair of the chip and the wire bonds to the chip and inner lead fingers.
Commonly, concentrated acids, such as sulfuric acid and nitric acid, or other solvents for the resin have been employed. Problems in prior art decapsulators and methods include difficulty in controlling the desired amount of etching, in removing debris formed in the etching process, in preventing damage to the package, including interior metallization, and in providing for adequate safety.
A decapsulator sold by BandG Enterprises, Inc. of Soquel, Calif., namely a Model 250, includes an appropriate acid resistant gasket sealed on an etch head, within which the device to be decapsulated is placed. A safety cover closes automatically when the process is started, clamping the device in place. The gasket on the etch head allows the chamber to be sealed and pressurized with nitrogen to approximately two PSI (pounds per square inch). The etching is started when a metering pump moves etchant from a heat exchanger located in plate with a sinuous passage into a cavity formed by the gasket, the device, and the etch head. The acid remains in the chamber for a short period of time, where it reacts with or attacks the encapsulant material. After the etchant has been allowed to work, the pump is activated again and a fresh volume of acid is moved into the cavity. This process continues until the desired amount of device exposure is achieved. When the integrated circuit is exposed at the end of the etch cycle, the pump runs continuously to flush the cavity. After this rinsing period, the entire system is purged with nitrogen, blowing all waste materials into a waste bottle. At the end of the process, the safety cover opens automatically, and the device is removed for post-etch cleaning.
While such decapsulation units do perform the necessary package removal, the use of mechanical pumps in the decapsulators adds significantly to their cost and thus the cost of IC device testing, including costs for repair and maintenance of the pumps. Further, the need to remove the device from its board in order to allow decapsulation in the decapsulator unit incurs a risk of shorting out the circuit and/or other forms of damage to the device. Further it is desirable to decapsulate the integrated circuit while the circuit is on a mother board or system card to better understand the failure mode as a function of system environment.
Accordingly, what is needed is a method and system for decapsulating plastic packages more efficiently and with greater ease. The present invention addresses such a need.
The present invention provides aspects for a decapsulation system and technique. In the present invention, a portable decapsulation system is provided beneath at least one integrated circuit device on a printed circuit board. Package decapsulation of the least one integrated circuit device occurs through acid blasting by the portable decapsulation system. The portable decapsulation system includes a beaker, fuming acid within the beaker, and a sealed fitting for the beaker and holding an electronic device being decapsulated. Capillaries within the sealed fitting through which the fuming acid is released acid blast the electronic device, and a waste tube coupled to the sealed fitting allows for removal of solid waste during the acid blast.
Through the present invention, a more efficient device decapsulation technique is provided that enhances the safety and ease of board level decapsulation. The decapsulation of the present invention requires no mechanical pump, thus reducing the cost as well as providing the advantage of allowing portable use. These and other advantages of the aspects of the present invention will be more fully understood in conjunction with the following detailed description and accompanying drawings.